Physiology and Pathophysiology of Pain

Question 1

what is pain?

Answer 1

unpleasant sensory and emotional experience which we primarily associate with tissue damage or describe in terms of such damage or both

Question 2

what is nociception?

Answer 2

The detection of tissue damage by specialized

transducers connected to A-delta and C fibers

Question 3

what do nociceptors respond to?

Answer 3

thermal, chemical, mechanical noxious stimuli

Question 4

what are the characteristics of A alpha and A beta fibres?

Answer 4

myelinated
large diameter
proprioception, light touch

Question 5

what are the characteristics of A delta fibres?

Answer 5

lightly myelinated
medium diameter
nocioception

Question 6

what are the characteristics of the C fibres?

Answer 6

unmyelinated
small diameter
innocouous temperature, itch
nociception

Question 7

which fibres conduct pain?

Answer 7

A delta and C fibres

Question 8

what is the spinothalamic tract?

Answer 8

major tract sending impulses to thalamus

Question 9

where are the cell bodies from the spinothalamic tract located?

Answer 9

Rexed lamina 1, 2, & 5

Question 10

what are the different types of spinothalamic tracts?

Answer 10

Lateral and ventral or neo and paleo STT

Question 11

where does the lateral STT terminate?

Answer 11

ventroposterior thalamic nuclei

Question 12

where does the ventroposterior thalamic nuclei primarily feed into?

Answer 12

somatosensory cortex to facilitate the spatial, temporal and intensity discrimination of painful stimuli.

Question 13

where does the medial thalamic nuclei recieves input from?

Answer 13

ventral spinothalamic tract

Question 14

what is the ‘second relay station’

Answer 14

thalamus

Question 15

what are the connections of the thalamus?

Answer 15

Cortex
Limbic system
Brainstem

Question 16

where does pain perception occur?

Answer 16

in somatosensory cortex

Question 17

what is hyperalgesia?

Answer 17

Increased perception of pain or even perception of non-noxious stimuli as noxious stimuli

Question 18

when does hyperalgesia happen?

Answer 18

whenever there is tissue injury and inflammation

Question 19

what is primary hyperalgesia?

Answer 19

is hyperalgesia at the site of injury

Question 20

what is secondary hyperalgesia?

Answer 20

hyperalgesia in the surrounding uninjured tissue

Question 21

what changes in nociceptor does allodynia cause?

Answer 21

decreased threshold for response

Question 22

what changes in nociceptor does hyperalgesia cause?

Answer 22

exaggerated response to normal and supranormal stimuli

Question 23

what changes in nociceptor does spontaneous pain cause?

Answer 23

spontaneous activity in nerve fibres

Question 24

what is central sensitisation?

Answer 24

It is the response of second order neurons in the CNS to normal input both noxious & non-noxious

Question 25

what are the 3 main concepts of central sensitisation?

Answer 25

wind-up classical long-term potentiation

Question 26

what does the wind up involve?

Answer 26

Involves only activated synapses Homosynaptic activity dependent progressive increase in response of the neurons Manifests over the course of stimuli & terminates with stimuli

Question 27

what does the classical involve?

Answer 27

Involves opening up of new synapses (silent nociceptors) Heterosynaptic activity dependent plasticity Immediate onset with appropriate stimuli Outlast the initial stimuli duration Can be maintained even at low levels of ongoing stimuli

Question 28

what does the long term potentiation involve?

Answer 28

Involves mainly the activated synapses Occurs primarily for very intense stimuli

Question 29

what are the differences in acute and chronic pain?

Answer 29

``` acute pain- physiological prescense of noxious stimuli serves protective function usually nociceptive ``` ``` chronic pain- pathologival prescence of noxious stimuli is not necessary does not serve any purpose nociceptive, neuropathic or mixed ```

Question 30

what is nociceptive pain?

Answer 30

A sensory experience that occurs when specific peripheral sensory neurones (nociceptors) respond to noxious stimuli

Question 31

when does nociceptive pain resolve?

Answer 31

when damaged tissue heals (bone fractures, burns)

Question 32

what is neuropathic pain?

Answer 32

Pain initiated or caused by a primary lesion or dysfunction in the somato-sensory nervous system

Question 33

is neuropathic pain usually acute or chronic?

Answer 33

almost always chronic condition

Question 34

does neuropathic pain respond well to analgesics?

Answer 34

no

Question 35

what increases the transduction in pain?

Answer 35

NSAIDs Ice Rest LA blocks

Question 36

what increases the transmission in pain?

Answer 36

``` Nerve blocks Drugs Opioids Anticonvulsants Surgery DREZ Cordotomy ```

Question 37

what improves the perception in pain?

Answer 37

``` Education Cognitive behavioural therapy Distraction Relaxation Graded motor imagery Mirror box therapy ```

Question 38

what improves the descending modulation?

Answer 38

``` Placebos Drugs Opioids Antidepressants Surgery Spinal cord stimulation ```